Facebook has a 10,000 disc Blu-ray changer that stores old data

One day, Facebook plans to move data that isn’t accessed all that frequently to so-called “cold” flash storage. Until then, they’re making do with a 10,000 disc Blu-ray changer that can handle a full petabyte of data.

That’s 10,000 pricey 100GB BD-R XL discs. They currently run around $45 or $50 per disc in stores, but you’d assume that an operation like TDK would give Zuck a price break for purchasing lots of a few thousand at a time.

Facebook’s automated beast fits into what sounds like a standard 42U server cabinet. Inside there’s a robotic disc-swapping mechanism that can shift the Blu-ray discs between storage stacks and one of 16 5.25″ burners.

Why not just use hard drives? Because they draw way more power. Facebook estimates that 80% less energy is required to store the same petabyte of data in one of these Blu-ray vaults instead of in a more conventional NAS box. The rack-mounted system also costs about 50% less to build.

Facebook says that the discs are used for data that hardly ever needs to be pulled up — including duplicate user photos and videos. A petabyte of data like that could be stored more cheaply on DLT: an 800GB cartridge sells for the same price as a single BD-R XL disc.

Access times aren’t generally great on linear media, though. If Facebook wanted to ensure that files could be retrieved with some speed, then optical discs were definitely the better choice. DLT drives are a heck of a lot more expensive than BD-XL burners, too.

The engineering team behind Facebook’s 10,000-disc storage tower no doubt weighed the pros and cons of several different configurations before settling on Blu-ray. They’re also convinced that manufacturers are going to figure out how to pack additional gigabytes onto those discs. When they do, it should be as simple as swapping in 16 new SATA burners to reap the benefits. They’re hoping to pack 5PB into a single rack in the near future. That’s a whole lotta selfies.